With the advent of semi-conductor technology and the consequent miniaturization of circuit designs, there are continuing needs for subminiature packaged passive electrical components that are machine insertable into printed circuit boards or other circuit supports. Many semi-conductor circuits and integrated circuits have been packaged in small plastic cases which are known as DIP's (Dual In-Line Packages) and which are machine insertable in, and mass solderable to, circuit boards. In the design of these complex miniature circuit packages, ceramic capacitor packages have been used because of their small size and adapability to machine insertion.
Rolled metallized film capacitors have had limited use in the newer miniature circuit designs because of their relatively large size and lack of susceptability to machine insertion.
However, rolled film capacitors possess certain desirable properties over ceramic capacitors such as precise capacitance value, stable frequency characteristics, long life and good stability under varying temperature and humidity operating conditions. These rolled film capacitors also possess the characteristic of forming an open in a circuit upon breakdown rather than a short circuit condition which results from a breakdown of a ceramic capacitor.
One of the problem areas in the development of miniature boxed rolled metallized film capacitors resides in providing terminations which may be assembled to rolled film capacitor blanks within small plastic boxes similar to the boxes used to package DIP's. Moreover, the terminations to a rolled film capacitor require that the terminations be made within a minimum introduction of added series resistance resulting from the bonding of terminals to the rolled film capacitor blank.
Numerous termination structures and methods of assembly have been developed to terminate rolled film capacitor blanks, but in general, these techniques are not concerned with terminating a capacitor blank within a small plastic box. U.S. Pat. No. 2,915,946 to J. Katzman discloses a pair of terminals having knurled or serrated sections which are wrapped with the metal foils of a paper-foil condenser to mechanically contact and terminate the respective foils. U.S. Pat. No. 3,243,675 to C. C. Rayburn shown a convolutely rolled capacitor that is terminated by pressing electrically heated wires into opposed ends of a metal foil-dielectric film capacitor blank to melt and shape portions of the dielectric films about the lead wires to secure the leads in contact with the metal foils. In present day commercial manufacture, a common expedient used to terminate rolled metallized film capacitors includes spraying a low melting point metal such as zinc against the opposite ends of the capacitor blank to form heat fusible end electrodes. Next, pretinned lead wires are heated and pressed against the end electrodes to metallurgically bond the leads to the end electrodes and, hence, to the metallized coatings on the respective rolled films.